"For me" with an Onx since 2015 the 1.5 -2 range is something i did try during first year but i was always worry about it going below 1.5, so ever since 2017 i have been using 2 - 2.5, my ideal number is 2, that is what works best "for me"'; do not see the need to play with below 2 numbers, it was stressful and something else to worry about , with the 2.0 - 2.5 i dont even think of warfarin as a problematic thing.
I think that you are wise to stay above 2.0. The study that is underway references the two previous studies which looked at lower INR range, the Proact Trial and Lowering It. Proact targeted 1.5-2.0, but there was tight INR control and the average INR for the test group was 1.89, actually very close to the 2.0 mark. This suggests to me that they were cautious to stay away from the 1.5 threshold. Lowering It, which had a target range of 1.5-2.5 for the test group had an average INR of 1.94. So, both of these trials had tight control and even though there was a low threshold of 1.5, it would appear that they probably steered clear of that. It is one thing to test weekdly and have the A Team working coagulation management. In the real world, many go 4-6 weeks between INR testing and they don't always have the A Team coagulation management in play, making it even more precarious.
These studies all play games with words as well, I have noticed. They will lump all bleeds together, not separating major bleeds from minor bleeds. Then then will say, the lower INR resulted in fewer bleeding events with no increases in strokes or heart attacks. But, when you look at the actual results you find that Lowering IT had 3x as many thrombolic events in the test group as compared to the control group. How then are they able to say that the stroke events were "similar" or the same? It is because due to relatively small numbers of participants and relatively short period of study, the number of thrombolic events was 3 for the test group and 1 for the control group. It is new math to say that there was no difference, but apparently they get a pass because the two are both relatively low numbers. Increase the number of participants by 10 fold and take the study out 20 years and they will not be able to say that there was no statisical differnce when the number is something like 100 thrombolic events vs 300.
" Two moderately-sized clinical studies showed that an INR target range of 1.5-2.5 resulted in less bleeding than the usual higher target range without increasing blood clot formation or stroke in patients with a newer valve model. "
Is this true? Not really. Lowering It found 3x as many thromboembolic events in the test group with the lower INR.
" One versus three thromboembolic events occurred in the LOW-INR and CONVENTIONAL-INR, respectively, .."
LOWERING-IT trial established that the proposed LOW-INR target is safe and feasible in low-risk patients after bileaflet aortic mechanical valve replacement. It results in similar thrombotic events and in a significant reduction of bleeding occurrence when compared to the conventional...
Look at how Proact uses new math to claim that a 60% increase in TE and thrombosis is "no different'
“…with no differences in the rates of TE and thrombosis events (2.96%/pt-yr in the test group versus 1.85%/pt-yr in the standard group, p = 0.178)”
The Prospective Randomized On-X Valve Anticoagulation Clinical Trial (PROACT): Lower is better, but is it good enough?
So, then in the new study, given the mathematical slight of hand, when referencing the two studies, they claim:
"..without increasing clot formation or stroke.."
Each have to make their own decision with the consultation of their medical team, but I would give some margin away from the 1.5 INR line.
Both studies found fewer bleeds in the lower INR group, but more strokes and heart attacks. Why not stick to the INR ranges that have the lowest events of all? Personally, I'd rather have a bleeding event than a stroke. That being said, some patients, who have issues with bleeding or are more prone to bleeding, might find that the trade off is worth it. I believe that these studies are valuable and give us important data. But, what I find troubling is that there appears to be bias in the presentation of the data favoring the sponsor of the studies economic interest in suggesting a lower INR is better. And, to be clear, the FDA in approving the lower INR for On-X, is not saying the lower INR is better. They just found that the number of events in that lower range to be reasonable.